Background: The study of viruses is inseparable from their host, and the relevance of the models is most often associated with the relevance of the results. Technological, ethical and legislative developments have led to the emergence of organoid models in many species. The study of equine herpesviruses could in turn benefit from this new approaches.

Objectives: The aim of this study is to validate a cerebral organoid model derived from equine reprogrammed pluripotent stem cells (ePSCs) in order to obtain a new relevant in vitro 3D model to study host-pathogen interactions, in particular neurotropic viruses.

Study Design: Development of new 3D models and proof of concepts.

Methods: Equine cerebral organoids (eCOs) were generated from ePSCs in neural induction medium and growned individually in wells. At D50, the eCOs were respectively infected with one of the three EHV-1 strains (A2254, G2254 and C2254) or with a reference EHV-4 strain at 10,000 or 1,000 pfu. After 5 days, nucleic acid extraction from organoids and their culture supernatants was performed and viral load of EHV-1 or EHV-4 was determined as previously described (doi: 10.1016/j.virol.2018.10.013)

Results: After 5 days post-contact with 10,000 pfu/ml, all organoids are positive for EHV-1 and the viral load increased by more than 3 Log. An increase of the viral load in the culture supernatant was also measured. The same observations were made after infection with 1,000 pfu/ml. Organoids appear to be also permissive for EHV-4 even if the strain seems to replicate less than the 3 EHV-1 strains.

Main Limitations: lack of specific antibodies for immunocytochemistry of eCOs.

Conclusions: These results show for the first time the capacity of eCOs model to replicate three different strains of EHV-1 and one EHV-4 strain opening the way for further cell-virus interactions studies in neural environment.